Plate type boiler



I Aug. 27, 1963 3 Sheets-Sheet 1 Filed Feb. 9. 1960 0 w a w y A o 4: a m P 9 a (1/114 2 m I F Q a/ m a a a i 7 6 W 3 7 a i fi 4 1 I M w m .6 H --b 4 3 a Q a m R. m M mM/ 0 m .0 v a A s s W a my C Aug. 27, 1963 c. c. SMITH PLATE TYPE- BOILER 3 Sheets-Sheet 3 Filed Feb. 9, 1960 I L l nouns-rar- 00:04 0 7-04 MMP IGNITION aka 7::- 7-04-747- IN V EN TOR.

4 TOR/V United States Patent 3,101,730 PLATE TYPE BUILER Clarence C. Smith, Oltemos, Micl1., assignor to Tranter Manufacturing, Inc, Lansing, Mich, a corporation of Michigan Filed Feb. 9, 1960, Ser. No. 7,581

7 Claims. (Cl. 165166) The present invention relates to an improved plate-type hot water boiler for space heating, as through the agency of heat transferring units, which boiler is of extremely simple and inexpensive fabricated construction as regards the water circulatory and heat transfer boiler unit proper thereof. The invention also concerns an improved combination of such plate boiler unit with a further heater unit for domestic water, in whicha heating coil of the last named unit is disposed in a water box or reservoir which is connected in water circulating relationship to the boiler, whereby the boiler water serves as a heating medium for a domestic water supply.

It is an object of the invention to provide a boiler unit and combination of the character referred to, in which the boiler unit is composed lsimply of one or more plate panels constituted alike by sheet metal plates welded, brazed or otherwise permanently bonded in face to face relation to one another and conformed to provide Water circulating headers and header-connecting passages between the plates.

Another object is to provide a boiler unit in which there are a plurality of such platepanels fixedly mounted and associated relative to one another in such manner that boiler water force-fed from a circulating pump is simultaneously caused to flow through these panels, subject to maximum heat transfer from hot products of combustion impinging the large surface area of these plate panel com ponents. The factors of large heat transfer surface and forced water circulation combine to produce maximum heating capacity for a given size boiler installation, and maximum heat transfer efiiciency.

Another object is to provide a multiple panel boiler unit as described which, as associated in combination with a domestic water heater unit of the character referred to, has provisions for a maximum efficiency circulation of boiler water therethrough, as well as to and through a water box of'the last named unit, within which water box a domestic water circulating coil is disposed to receive heat from the boiler water entering the box.

More specifically, it is an object of the invention to provide a plate type boiler unit fabricated of assembled and welded, brazed or otherwise permanently bonded plate panels as described, which panels are of generally similar construction in regard to the formation of intake and discharge headers and parallel connecting passages therein, whereby the invention makes possible the very expeditious and inexpensive production of more or less standard panels for different sizes or capacities.

Yet another specific object is to provide a boiler unit including water circulating and heat transfer plate panels arranged in an outline which is hollow, with cross-over plate panels of generally similar construction disposed in the hollow to receive heat from hot gaseous products of combustion of a suitable burner therebeneath.

A still further object is to provide a space and domestic water heating installation including boiler and water heating components as mentioned above, which system has a pump-forced flow of water through both the space heating and water heating units thereof for the highest possible ratio and efficiency of heat transfer; and in which, in accordance with a further improvement, thermostatically controlled by-pass means are provided to seasonally limit the flow of boiler water \to the boiler unit and water box of the domestic water heater, to the exclusion of the ex- "ice ternal space heating unit. Thermostatically controlled components automatically govern such by-passing, as in the summer months, as well as automatically governing the cutting in and out of the'pump and burner of the system.

The foregoing as well as other objects will become more apparent as this description proceeds, especially when considered in connection with the accompanying drawings illustrating preferred embodiments of the invention wherein:

FIG. 1 is a schematic front elevational view showing the improved boiler and various associated pump, burner, control and other components as mounted within a suitable outer shell or housing, the front panel of which is removed;

FIG. 2 is a schematic view in vertical, front-to-rear section through the boiler, showing its basic burner, fire box and heat transfer components;

FIG. 3 is :a fragmentary perspective, as viewed from the left hand and from beneath, illustrating the plate type construction of typical water-circulating, heat transfer panel means in accordance with the invention;

FIGS. 4 and 5 are fragmentary views respectively in horizontal cross section on line 4-4 of FIGS. 3 and 8, and in vertical cross section on line 5-5 of those figures;

FIG. 6 is a schematic fragmentary view in front elevation of the plate-type water circulating and heat transfer panel structure of the boiler;

FIGS. 7 and 8 are similar fragmentary views of this structure in rear and side elevation, respectively;

FIG. 9 is a top plan view of the plate boiler unit;

FIG. 10 is a fragmentary front elevational view, partially broken away and in vertical section, of a domestic water heater which is an auxiliary component of the boiler'disposed at the front and top thereof;

FIG. 11 is a side elevational view, partially broken away and vertically sectioned, of this domestic water heater; and

FIG. 12 is a schematic wiring diagram for the pump, burner and controls of the boiler of the invention.

=First referring to FIG. 1 of the drawings, the improved boiler is generally designated as awhole by the reference numeral 10, being encased in an inner housing 11, the front wall of which is of suitably rigid construction to support various valve, burner and control instrumentalities to be hereinafter described. This inner housing is in turn suitably mounted by means of uprights 12 within an outer sheet metal shell or housing 13, so that all operating components are enclosed, although readily accessible upon removal of a front panel (not shown) of housing 13.

Essential operating and control components associated with the boiler 10, as shown in FIG. 1, are a suitable conventional burner 15 of the oil or gas fueled type, with which the invention is not concerned; a water circulating pump r16 adapted to be driven by an appropriate electric motor 17 mounted in front of the front wall of inner housing 11, a boiler water inlet or supply pipe or conduit 18 leading downwardly from the discharge side of pump 16 to the intake of the boiler heat exchange and circulating plate unit, to be described, the intake side of pump 16 having connected thereto a further return pipe or conduit 19 from a radiating system of one sort or another; and a thermostatically governed water valve 20 disposed in a discharge line 21 which leads from the domestic water heater box of the invention (to be described) to the heat radiating system supplied by the boiler. A valve element 28 of the valve 20 automatically closes when boiler Water temperature reaches a predetermined value, thereby by-passing the flow of water from boiler water discharge line 21 through a by-pass tube 29 to the intake side of pump 16. Such system, although it is not shown and is no part of the invention, may be considered to be in the form of appropriate, hot water circulating, wall baseboard radiator units or other heat transferring units. It will be understood that the supply line 19 to pump 16 receives return water from such radiator unit.

Other components which appear in FIG. 1 of the drawings are an appropriate protective unit or protectostat 23 wired (as shown in FIG. 12), for the purpose of cutting off the operation of burner 15 on ignition failure; a thermostatic relay control or aquastat relay 24 carried on a side wall of outer housing '13, and having a suitable connection 25 to a thermostatic bulb or like heat-sensing device 25, for the purpose of cutting off the operation of burner 15 at a maximum water temperature limit; a domestic water heat control unit or aquastat 26; a protective thermostatic relay control or protectorelay 27 carried by the side wall housing 13; and domestic water circulating pipes or lines 31, 32, the former a return line to and the latter a supply line from a domestic water heater unit (to be described) these lines servicing the domestic water system of a residence or the like in which the boiler is installed in the usual way.

lF-urther shown in FIG. 1 are an appropriate pressuretemperature gauge device 33 and pressure relief valve 33', not germane to the invention, and an air vent or vent line 34 of the domestic water heater unit. The reference numeral 36 in FIG. 1 designates a suitable observation cover applied to the forward wall of the boiler '10. As appears in FIG. 12, the burner 15 is equipped with a suitable conventional, electrically controlled ignition device 35, appropriately wired therewith and with the remaining electrically controlled components of the system. Also shown in FIG. 12 is a standard room thermostat 37.

The reference numeral 38 in FIGS. 2 and 6 generally designates the improved plate type, water circulating and heat transfer boiler unit of the boiler of the invention. It is constituted by plural water circulating and heat transfer panels of similar plate construction, as will be described. The reference numeral 39 designates a fire box (-FIG. 2) mounted within the inner boiler housing 11 adjacent its rear wall, and directly beneath the above-mentioned heat transfer components of the boiler unit 38; and the reference numeral 40 (FIGS. 2, 10 and 11) generally designates the domestic water heater unit associated with the boiler of the invention. Products of combustion of the burner discharge rearwardly and upwardly through inner housing .11, rising past the plate boiler components and exhausting rearwardly through a suitable flue 41 at the top and rear of the housing means. In transferring heat to the plate unit 38 the hot burner gases are channeled between vertical bafiles 42, and a certain portion of these gases rise forwardly and upwardly past domestic water heater 40 to heat the contents of the latter.

Structural features of the improved plate-type Water circulating and heat exchange unit 38 are best shown in FIGS. 3, 4 and 5 of the drawings. It is made up, as will hereinafter be described in greater detail, of front crossover and rear and side panels, fabricated of a pair of rectangular sheet metal plates 44, 45. The former is flat throughout, while the latter is embossed to provide water circulatory passages between the plates when they are assembled in fiatwise face-to-fiace engagement. Thus the plate 45 is shown embossed to provide elongate vertical formations 46 paralleling one another which are of triangular cross section so that, when the plate 45 is welded, bnazed or otherwise permanently bonded to the plate 44 between and on opposite sides of these formations 46, water circulating passages 47 will be provided which are of generally triangular cross section.

In addition to this, the plate 45 is embossed in a direction at a right angle to the vertical formations 46 to provide further transverse or horizontal header formations of larger flow capacity, such as an upper horizontal header '48 and a similar lower header 49 (FIG. 6) paralleling it at opposite ends of the formations 46. The header formations 48, 49 are of rectangular channel-shaped outline, so that as welded, brazed or otherwise permanently bonded to the plate 44 on either side of such formations, header passages 50 are defined, into which the vertical circulatory passages 47 open at either end of the formations 46. It is to be understood that the plates 44, 45 are also welded, brazed or otherwise permanently bonded about their outer periphery, as at the marginal flange 51.

A plate-type water circulating and heat transfer panel unit 3-3 is thus constituted which has a large area for heat transfer from the hot products of combustion of the fire box 39. Structural plate features such as have been described in connection with FIGS. 3, 4 and 5 will, as appropriately supported within housing 11, result in the production of an upright, front cross-over plate panel, generally designated by the reference numeral 53, which is of limited height and as to which it will be observed that there are six of the vertical formations 46 providing individual circulatory passages 47.

FIG. 7 illustrates a rear plate panel generally designated by the reference numeral 55. It is constituted by component plates shaped and assembled in exactly the same manner as described above in connection with FIGS. 4 through 6, save for the fact that the rear panel 55 is of more elongated vertical dimensions than the front cross-over plate panel 53. Accordingly, its parallel passage formation and headers will be designated by reference numerals corresponding to those applied to corresponding parts and relationships in FIG. 6, but in this instance primed.

The same situation exists in reference to a pair of side plate panels, generally designated 56 and 57, which are substantially coextensive in height with the rear panel 55, paralleling and extending between opposite sides of the cross-over and rear panels 53, 55, in laterally outwardly spaced relation to the latter. Accordingly, since again structural features of the components of these panels 56, 57 are as described in connection with FIGS. 3, 4 and 5, corresponding reference numerals, double primed, will be employed to designate corresponding parts and relationships.

It will, however, be noted in FIG. 8 that the side panels 56, 57 have the respective lower headers 49" located intermediate the vertical length of the parallel passage formations 46", which open, therefore, into the top and bottom of the lower header 49, and upwardly into the top header 48". Moreover, as appears in FIGS. 6 and 8, each of the lower headers 49" has a flow restrictor 59 extending along the length thereof, in such manner that only a portion of the liquid flow upwardly in each of the side plate panels 56, 57 will be diverted by these restrictors laterally outwardly of the headers 49", the remainder continuing upwardly to the upper header 48" of the side panels 56, 57.

As illustrated in FIGS. 6 and 7, the side plate panels 56, 57 are bent at their lower ends to provide integral laterally inwardly directed extensions 61, 62, respectively, forming, in effect, a bottom panel for boiler unit 38, which has the same structural characteristics \as the panels 56, 57, as to the passages 47 typically shown in FIGS. 3, 4 and 5. The inner ends of these bottom-forming extensions communicate with a central, front-to-rear extending, bottom distributor header 63, which is medially connected by an L-shaped fitting to a boiler intake pipe, which is the discharge pipe or line 18 of the circulating pump 16 (FIG. 1).

As shown in FIGS. 7 and 8, the rear end of bottom distributor header 63 is communicated by means of an L-shaped, tube 64 with the bottom header 49' of the back plate panel 55, so that water supplied to the header 49' will branch laterally therein and circulate upwardly through the formations 46 providing vertical passages of the panel 55. These passages discharge upwardly into the top header 48 of back panel 55; and this header is communicated at its opposite ends through 90" laterally and forwardly extending tubes 68, 69 with the rear end of each of the top headers 48' of the side panels 56, 57.

All boiler water received in. the headers '48" is delivered through pipes 71, 72 extending laterally inwardly from eludes boiler water which passes upwardly in: the side panels 56, 57 past the flow restrictors 59, water flowing upwardly through the cross-over plate panel 53 (FIG. 6), and water flow-ing upwardly in certain furthercross-over plate panels, located in the space between panels 53, 55, 5 6 and 57 and now to be described.

The water whichtravels upwardly in the side plate panels 56, 57 and is diverted laterally inwardly by the flow restrictors 59 of lower side panel headers 49", passes through pipes 74 man arrangement of upright cross-over plate panels, of which, as illustrated inFIGS. 2 and 9, there are four in the illustratedembodiment, the forwardmost being the front cross-over panel, These panels are all coextensive in height, and are shown in a front-to-rear staggered arrangement in FIG. 9, being designated 53, 77, 78 and 79. It is to be noted that the panels 53, 78 will receive water at the bottom thereof from pipes 74 communicating with the lower header 49" of a side plate panel 57 on one side of the boiler unit 38; while the alternate cross-over plates 77 and 79 will be supplied at their bottom through like pipes 74 from the lower header 49 of. the side panel 56 on the opposite sideof the unit. The upper ends of each of the cross-over plates 53, 77, 78, -79flcharge laterally outwardly through pipes 80, 81 to the upper headers 48" of the respective side plate panels 56, 57, from which the'flow is, as described above,xt hrough pipes 71, 72 to the domestic water heater 4t Thus, it is seen that the boiler unit 38 provides a very high surface area .for heat transfer at its front cross-over plate panel 53, its full height rear plate panel 55, its full length side panels 56, 57 and their respective inward bottom extensions 61, 62, and through the cross-overplate panels 53, 77, 78 and 79. The sectional character of 6 sealed communication with an intake line 31 from the domestic water system, and the coil portion 86 is fitted to the discharge line 32 to that system. A boiler front plate -87is provided which is removable for the purpose of installing hot water coil 85.

As indicated above, the improvement contemplates safety provisions controlled by the thermally responsive valve 20 in the boiler discharge line 21 to the space heating radiator (not shown) whereby as controlled by the domestic water control 26 the valve element 28 of'valve 20 may be closed, causing water to be by-passed through the tube 29 to the intake side of circulating pump 16, without traversing the radiator.

The hot water box 83 at the upper front of the boilerunit 38 acts as a collection point for all of the water goingthrough the boiler and also houses the domestic water coil 85. The lower part of the front boiler housing wall provides means for mounting the valve, burner, etc., and has a fire observation opening with cover 36. i

The incorporation of the domestic water unit in the boiler eliminates the necessity for a hot water heater, "and, in addition, makes possible the forced circulation of boiler water across its coil 85, fora very eificient heat transfer. 1

The boiler may be merchandized as a complete package, which includes thecontrols, pump, and burner, as well as'without these latter items.

The wiring for the electrically controlled components of the boiler is shown in FIG. 12, and such wiring provisions will be of a nature understood by those skilled in the art, with conventional electrical connections to the various pump, burner, thermostatically governed relay units and the like. I

In operation, for example, in the wintertime, when the room thermostat 37 calls for heat,the aquastat relay control 24 is actuated, which results inelectrical energization of the pump 16 and burner 15. As the boilerwater reaches a desired temperature, torexample about 185 F,

. "the thermostatic water valve 20 will be opened. Circulathese cross-over panels is as indicated in FIGS. 3, 4 and v 5, it being understood that they will be characterized by upper and lower header formations corresponding'to the header formations 48,49, and by connecting circulating passages provided by formations corresponding to the .7

formations 46.

Forced water circulation through all of the plate panel components is an important feature of the invention con:

tributing to high heat transfer capacity and elficiency. The entire boiler construction may be fabricated inexpensively of sheet metal stampings welded, brazed or permanently bonded together; and with'the above described basic standardized design the boiler may be made up in a large range of sizes and capacities for use as determined by the demand;

The hot gases from the burner fire box 39 circulate upwardly past the panel components of boiler unit 38 and between bafiles 42, also forwardly past the domestic V heater 40. The water is circulated positively by pump 16 through these components, thence through pipes 71, 72 to opposite sides of the heater 40, discharging from said heater through the pipe 21 to the radiation means of the space heating system (not shown). Return is through pipe 19 to pump 16, and then through the line 18 back to the bottom intake at header 63 of the boiler unit 38. i

The nature of the domestic water heater 40 is illustrated in FIGS. 10 and 11. It comprises a suitably sealed water reservoir or box 83into which the-pipes 71, 72 from the side panel top headers 48" discharge. Heater 40 further comprises a circulating coil 85 formed in a verticaltion through boiler'unit 38, domestic water heater 41 its discharge line 21 and return from the space heating radiator system to the pump 16 through line 1? is maintained until room thermostat 37 is satisfied. At this time the relay control 24 is actuated to shut oil burner 15; and

when the water temperature in boiler 38 drops below, say, 180 F., the thermostatic water valve 20 will close. In no event will it open unless the room thermostat is I calling for heat.

1801 F., whereupon the thermostatic water valve 20 closes, and all of the heat from the burner will go to ly flattened-contour (FIG. ll) and'disposed within the water box 83,including'central and upper coil portions 86 within its top extension 84. One end of the coil is in heat the domestic water coil 85.

In summertime operation the room thermostat does not call for heat and the thermostatic water valve 20 is always closed, bypassing water to pump 16. When domestic hot water is drawn, the aquastat domestic water control 26 'is actuated, which turns on p-ump '16 and burner 15, allowing the boiler 38, to cycle on and oil, thus 'to maintain water temperature in the boiler between limits of, say, F. to F.

The by-pass tube connection 29 between boiler unit 38 and thermostatically controlled water valve 20 on the discharge line 21 of the boiler, and between the radiator system and the circulating pump 16 on the inlet side of the boiler, results, when the valve20 is closed and the burnerand pump are in operation, in a definite forced circulation through boiler 38, but not through the radiating system.

In the interest of safety, should ignition of fuel oil or gas at theburner not take place, the protectostat 23 will "actuate the relay control 27 and shut off burner 15.

j Whenever the water in boiler 38 reaches its maximum temperature of, say 210 F., bulb 25' will sense it and 7 the aquastat relay control 24 will be actuated to shut off the burner.

What I claim as my invention is:

1. An upright plate type boiler comprising a pair of opposed upright, generally parallel, front and rear fluid circulating panel units spaced transversely from one another, a pair of opposed upright, generally parallel side panel units of a construction generally similar to said front and rear units, said front, rear and side units being arranged about the four sides of a boiler heating space, said panel units each comprising a pair of plates secured together in face-to-face sealed relation and providing therebetween a plurality of upright fluid flow passages and transversely extending, vertically spaced headers in communication with said passages adjacent vertically spaced points of the latter, the respective upper and lower headers of the respective units being in communication with one another, and at least one upright cross-over circulatory unit disposed between the opposed panel units of one of said pairs, said cross-over circulatory unit having a construction similar to said panel units, including vertically spaced headers in communication with one another through upright fluid flow passages, said headers of the cross-over unit being respectively in communication with at least one of said last named oppose-d panel units at the respective vertically spaced headers of the latter.

2. An upright plate type boiler comprising a pair of opposed upright, generally parallel, front and rear fluid circulating panel units spaced transversely from.one another, a pair of opposed upright, generally parallel side panel units of la. construction generally similar to said front and rear units, said front, rear and side units being arranged about the four sides of a boiler heating space, said panel units each comprising a pair of plates secured together in face-to-face sealed relation and providing therebetween a plurality of upright fluid flow passages and transversely extending, vertically spaced and substantially horizontal headers in communication with said passages adjacent vertically spaced points of the latter, and at least one upright cross-over circulatory unit disposed between the opposed panel units of one of said pairs, said cross-over circulatory unit having a construction similar to said panel units, including vertically spaced headers in communication with one another through upright fluid flow passages, said headers of the cross-over unit being respectively in communication with at least one of said last named opposed panel units at the respective vertically spaced headers of the latter, the respective upper and lower headers of the respective panel units being in comr munication with oneanother at the respective transverse header ends, thelower header of said front panel unit having communication with opposite ends of the lower headers of said side panel units at points substantially above thel'ower header of said rear panel unit.

3. An upright plate type boiler comprising a pair of opposed upright, generally parallel, front and rear fluid circulating panel units spaced transversely from one another, said rear unit being of substantially the full height of said boiler, said front unit being of lesser height, a pair of opposed upright, generally parallel side panel units of a construction generally similar to said front and rear units and of a height approximating that of the rear unit, said front, rear and side units being arranged about the four sides of a boiler heating space, said panel units each comprising a pair of plates secured together in face-toface sealed relation and providing therebetween a plurality of upright fluid flow passages and transversely extending, vertically spaced and substantially horizontal headers in communication with said passages adjacent vertically spaced points of the latter, and at least one upright cross-over circulatory unit disposed between the opposed panel units of said first named pair, said crossover circulatory unit having a construction similar to said panel units, including vertically spaced headers in communication with one another through upright fluid flow passages, said headers of the cross-over unit being respectively in communication with at least one of said last named opposed panel units at the respective vertically spaced headers of the latter, the respective upper and lower headers of the respective panel units being in communication with one another, the lower header of said front panel unit having communication with the lower headers of said side panel units at points substantially above the lower header of said rear panel unit, all of the upper headers having communication with one another at approximately the same level.

4. An upright plate type boiler comprising a pair of opposed upright, generally parallel, front and rear fluid circulating panel units spaced transversely from one another, said rear unit being of substantially the full height of said boiler, said front unit being of lesser height, a pair of opposed upright, generally parallel side panel units of a construction generally similar to said front and rear units and of a height approximating that of the rear unit, said front, rear and side units being arranged about the four sides of a boiler heating space, said panel units each comprising a pair of plates secured together in face-tof-ace sealed relation and providing therebetween a plurality of upright fluid flow passages and transversely extending, vertically spaced and substantially horizontal headers in communication with said passages adjacent vertically spaced points of the latter, and at least one upright cross-over circulatory unit disposed between the opposed panel units of said first named pair, said crosscver circulatory unit having a construction similar to said panel units, including vertically spaced headers in communication with one another through upright fluid flow passages, said headers of the cross-over unit being respectively in communication with at least one of said last named opposed panel units at the respective vertically spaced headers of the latter, the respective upper and lower headers of the respective panel units being in communication with one another, the lower header of said front panel unit having communication with the lower headers of said side panel units at points substantially above the lower header of said rear panel unit, all of the upper headers having communication with one another at approximately the same level, said side and rear panel units having means to communicate the headers thereof with a fluid circulatory line beneath the respective headers.

5. An upright plate type boiler comprising an upright fluid circulating panel unit, a pair of opposed upright, generally parallel side panel units of a construction generally similar to said first named unit and disposed in planes in substantially relationship to the plane of said first named unit adjacent opposite sides of the latter to substantially define three sides of a boiler heating space, said panel units each comprising a pair of plates secured together in face-to-face sealed relation and providing therebetween a plurality of upright fluid flow passages iand transversely extending, Vertically spaced headers in communication with said passages adjacent vertically spaced points of the latter, the respective upper and lower headers of the respective units being in communication with one another, and a pair of upright cross-over circulatory units disposed in substantially parallel planes between said opposed side panel units, said cross-over units being respectively alternately in communication with said side panel units at the respective vertically spaced headers thereof.

6. An upright plate type boiler comprising a pair of opposed upright generally parallel, front and rear fluid circulating panel units spaced transversely from one another, a pair of opposed upright, generally parallel side panel units of a construction generally similar to said front and rear units, said front, rear and side units being arranged about the four sides ofv a boiler heating space, said .panel units each comprising a pair of plates secured together in face-to-face sealed relation and providing therebetween a plurality of upright fluid flow passages and transversely extending, vertically spaced headers in communication with said passages adjacent vertically spaced points of the latter, the respective upper and lower headers of the respective units being in communication with one another, and at least one upright cross-over circulatory unit disposed between the opposed panel units of one of said pairs, said cross-over circulatory unit having a construction similar to said panel units, including vertically spaced headers in communication with one another through upright fluid flow passages, said headers of the cross-over unit being respectively in communication with at least one of said last named opposed panel units at the respective vertically spaced headers of the latter, the panel unit with which said cross-over unit communicates being provided adjacent its lower header with connecting means placing said last named lower header in communication with the lower header of the cross-over unit.

7. An upright plate type boiler comprising a pair of opposed upright generally parallel, front and rear fluid circulating panel units spaced transversely from one another, a pair of opposed upright, generally parallel side panel units of a construction generally similar to said front and rear units, said front, rear and side units being arranged about the four sides of a boiler heating space, said panel units each comprising a pair of plates secured together in face-to-face sealed relation and providing therebetween a plurality of upright fluid flow passages and transversely extending, vertically spaced headers in 30 communication with said passages adjacent vertically spaced points of the latter, the respective upper and lower cates being provided adjacent its lower header with connecting means placing said last named lower header in communication with the lower header of the cross-over unit, and with means to divert a portion of the fluid flow in said panel unit into said connecting means.

References Cited in the file of this patent UNITED STATES PATENTS 419,389 Whitelow Jan. 14, 1890 1,075,700 Doll Oct. 14, 1913 1,210,161 Gorr Dec. 26, 1916 1,611,764 Mendelson Dec. 21, 1926 1,667,795 Morrow May 1, 1928 1,820,901 Bernhard Sept. 1, 1931 1,865,958 Prinz July 5, 1932 2,100,772 Beck Nov. 30, 1937 2,200,426 Lahrnan May 14, 1940 2,607,535 Moore Aug. 19, 1952 

1. AN UPRIGHT PLATE TYPE BOILER COMPRISING A PAIR OF OPPOSED UPRIGHT, GENERALLY PARALLEL, FRONT AND REAR FLUID CIRCULATING PANEL UNITS SPACED TRANSVERSELY FROM ONE ANOTHER, A PAIR OF OPPOSED UPRIGHT, GENERALLY PARALLEL SIDE PANEL UNITS OF A CONSTRUCTION GENERALLY SIMILAR TO SAID FRONT AND REAR UNITS, SAID FRONT, REAR AND SIDE UNITS BEING ARRANGED ABOUT THE FOUR SIDES OF A BOILER HEATING SPACE, SAID PANEL UNITS EACH COMPRISING A PAIR OF PLATES SECURED TOGETHER IN FACE-TO-FACE SEALED RELATION AND PROVIDING THEREBETWEEN A PLURALITY OF UPRIGHT FLUID FLOW PASSAGES AND TRANSVERSELY EXTENDING, VERTICALLY SPACED HEADERS IN COMMUNICATION WITH SAID PASSAGES ADJACENT VERTICALLY SPACED POINTS OF THE LATTER, THE RESPECTIVE UPPER AND LOWER HEADERS OF THE RESPECTIVE UNITS BEING IN COMMUNICATION WITH ONE ANOTHER, AND AT LEAST ONE UPRIGHT CROSS-OVER CIRCULATORY UNIT DISPOSED BETWEEN THE OPPOSED PANEL UNITS OF ONE OF SAID PAIRS, SAID CROSS-OVER CIRCULATORY UNIT HAVING A CONSTRUCTION SIMILAR TO SAID PANEL UNITS, INCLUDING VERTICALLY SPACED HEADERS IN COMMUNICATION WITH ONE ANOTHER THROUGH UPRIGHT FLUID FLOW PASSAGES, SAID HEADERS OF THE CROSS-OVER UNIT BEIN RESPECTIVELY IN COMMUNICATION WITH AT LEAST ONE OF SAID LAST NAMED OPPOSED PANEL UNITS AT THE RESPECTIVE VERTICALLY SPACED HEADERS OF THE LATTER. 